| 1. |
- Abom, A.E., et al.
(författare)
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Characterization of the metal-insulator interface of field-effect chemical sensors
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:12, s. 9760-9768
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Tidskriftsartikel (refereegranskat)abstract
- The metal-insulator interface of hydrogen-sensitive metal-insulator-semiconductor capacitors, with SiO2 as the insulator and Pt as the metal contact, was discussed. It was found that the difference in hydrogen response between differently prepared devices was explained by a difference in concentration of available adsorption sites. The analysis showed that the concentration of Pt atoms in contact with the oxide affected both the hydrogen response and the metal-oxide adhesion.
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| 2. |
- Abom, A.E., et al.
(författare)
-
Experimental evidence for a dissociation mechanism in NH3 detection with MIS field-effect devices
- 2003
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Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 89:1-2
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Tidskriftsartikel (refereegranskat)abstract
- The gas response mechanism of ammonia detection with Pt-based metal-insulator-semiconductor (MIS) field-effect sensors was investigated. An experimental model system was designed which compares the responses of thick continuous Pt layers with controlled morphology and surface chemical composition, with the response of thin, discontinuous layers. The surface of a thick, continuous sputter-deposited Pt film is modified, either by (i) the deposition of a thin SiO2 overlayer, (ii) reactive sputter deposition of PtOx, or (iii) co-deposition of Pt with SiO2 in Ar + O2 atmospheres. We show that the ammonia response is caused by the formation of atomic hydrogen through the dissociation of NH3 at temperatures <200 °C. It is found that the modified surfaces exhibit increased ammonia selectivity compared to a pure Pt film. Results from this work indicate that the reason for the changed selectivity is the appearance of an oxidized PtOx phase or triple phase boundaries between Pt, SiO2 and the ambient gas, rather than for solely morphological reasons. © 2002 Elsevier Science B.V. All rights reserved.
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| 3. |
- Abom, A.E., et al.
(författare)
-
Influence of gate metal film growth parameters on the properties of gas sensitive field-effect devices
- 2002
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 409:2, s. 233-242
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of Pt have been grown as gate metals on the oxide surface of gas sensitive field-effect devices. Both electron beam evaporation and dc magnetron sputtering has been used. The energy of the impinging Pt atoms, the substrate temperature and the thickness of the Pt film were used as parameters in this study. The influence of the growth parameters on the gas response has been investigated and compared with the properties of the films, studied by transmission electron microscopy, Auger electron spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The conditions during growth of the Pt film are found to have a large impact on the properties of the device. As expected, crystallinity, morphology and the metal/substrate interfacial structure are also affected by processing parameters. Three different growth processes stand out as the most promising from gas sensor considerations, namely room temperature evaporation, sputtering at high pressures and sputtering at high temperatures. The correlation between gas responses and properties of the gas sensitive layer is discussed. © 2002 Elsevier Science B.V. All rights reserved.
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| 4. |
- Abom, A.E., et al.
(författare)
-
Thin oxide films as surface modifiers of MIS field effect gas sensors
- 2002
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Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 85:1-2, s. 109-119
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic activity at the surface of Pt based MIS field effect gas sensors is modified by the deposition of thin films of SnO2, Al2O3 and SiO2, grown by reactive sputtering. It is found that a very thin layer (<10 nm) of SiO2 and SnO2 changes the catalytic activity towards higher NH3 selectivity, but with thicker films the sensor response vanishes. Since the response mechanism for these sensors is dependent on dissociation of molecules, it is likely that at low temperatures (140 °C), neither dissociation on nor transport/diffusion through the thicker films takes place. However, with Pt in conjunction with SiO2 or SnO2, the surface reactions will be altered, with enhanced NH3 selectivity as a result. A thin film of Al2O3, on the other hand, has a much smaller influence on the gas response to the test gases used in this work. Furthermore the sputtering process is found to strongly influence the sensor responses, and specifically reduce the sensitivity of the sensor. A thin intermediate layer of evaporated Pt does not completely protect the underlying structure from sputter induced damage. © 2002 Elsevier Science B.V. All rights reserved.
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